CA2039302C - Filter cell sheet installations - Google Patents

Abstract

Automatic backwash filter systems including a filter tank divided into a multiplicity of seriate cells of substantially the same width by a plurality of vertical rectangular cell sheets are improved by provision of new spacer assemblies to mitigate bowing of the cell sheets during backwashing or other operations applied to the cells. Such spacer assemblies include horizontally aligned bores that extend through each cell sheet adjacent their top, one or more stringers that extend through the bores, and a plurality of tubes of approximately the same length substantially equal to the width of the cells.
One of such tubes is positioned in each filter cell surrounding the stringer present in such cell and between the surfaces of the respective cell sheets.
Where a plurality of stringers are used in the spacer assemblies arrangements are disclosed for making final connections to complete the assemblies.

Description

BACKGROUND OF THE INVENrrION

2 1. Field of the Invention 3 This application relates broadly to ~ ruvements in automatic4 backwash filtering sy~lellls. More particularly, it concerns illlploved filter cell sheet installations in such systems.
6 2. D~s.,,il,lion of the PriorArt 7 A~ltom~tic backwash filter sy~lems are known in the art as exemplified 8 in U.S. patent Nos. 3,239,061; 4,133,766; 4,617,131 and 4,764,288 currently g assigned to Infilco Degremont Inc., the assignee of the invention disclosed herein. Such systems are further exemplified in Infilco Degremont's brochure 11 DB-370, dated May, 1989, entitled ABW~ Automatic Backwash Filter. The 12 disclosures of these patents and the brochure are incorporated herein by 13 reference.
14 In the backwash filter sy~lems, cell sheets that divide the total filter bed into compartmented filter cells have a tendency to deflect (bow) when the 16 cells are being backwashed. The resulting movement can cause seals 17 associated with porous rigid plates, that are fixed at a level between the upper 18 and lower ends of the cell sheets and l~ans~el~e thereto, to fail allowing a 19 media leak. In other cases, the cell sheets may bow towards each other which causes high backwash flow rates that, in turn, promotes media loss through the 21 washwater systems. When the cell sheets bow away from each other, the 22 backwash flow rate is reduced c~ ing insufficient media ~ n~ion, hence23 allowing the media to become dirty. Of course, poor installation caused by 24 difficulties in handling of parts forming the systems can also result in cell sheet bowage.
26 In an effort to mitigate the bowage problems with cell sheets in the 2 7 subject filter sy~lenls, filter manufactures and fabricators, have resorted to use 28 of nut and bolt tie rod assemblies. Each such assembly requires two holes in 29 the cell sheet, a rod, four washers and four nuts. Each assembly must be put together one piece at a time, a precise measurement must be made and all 31 nuts must be locked. Any such assembly which is not completely tight can be 32 loosened and negate its purpose. Also if strict attention is not paid to 33 measurements, col-lp~ssive forces can allow sheets to bow.
34 The present invention addresses the problem of cell sheet bowage in automatic backwash filter systems and provides improved installations for the - 2 - *

` 2039302 cell sheets that greatly simplify cell sheet inet~ tion, reduce the number of required parts, miti~te me~ .tment requirements and reduce assembly costs.
A principal object of the invention is the provision of 5 i~ rovements in ~ltom~tic backwash filt~oring systems.
Another object is the provision of i~ roved filter cell sheet inet~ tions in such systems.
Further objects inclll(le the ~imr~lification of prior methods of ~esemhly of cell sheets in such filter systems, reduction in the number of 0 parts required for cell sheet inet~ tion miti~tion of problems previously associated with need for high ~tt~ntion to inst~ tion me~ el~ents and reduction in assembly costs.
Other objects and further scope of applicability of the present invention will become a~c;lll from the detailed descriptions given herein;
5 it should be understood, how~vel, that the detailed descriptions, while indicating plefelled embo-limente of the invention, are given by way of illustration only, since various ch~nges and modifications within the spirit and scope of the invention will become apparelll from such descriptions.
A construction in accordance with the present invention incllldes 20 improvements in an automatic backwash filter system including a ter tank de_ned by a bottom, _rst and second opposed, parallel side walls and third and fourth opposed parallel side walls divided into a mnltiplicity of seriate cells of subst~nti~lly the same width W by a plurality of subst~nti~slly vertical rect~n~ r cell sheets defined by a top edge, a bottom edge, a pair 25 of side edges, a first exposed snrf~ce on one side and a second exposed surface on the other side of each cell sheet, the cell sheets running parallel to the first and second side walls, each of the cells cn~ -il,g a ho, ;~ol~lfll rigid porous filter plate located between the exposed surfaces of its r~speclive cell sheets at a position above the tank bottom, filter media 3 o contained in the cells and supported on the porous plates, infln~nt means for delivering liquid to be filtered to the top of the filter media and effl~lent means for discha~ g liquid filtered through the media and the plates from the filter system at a level below the plates, the improvement which compri~es7 spacer means to mitig~te bowing of the cell sheets, the spacer 35 means including bores exten~lin~ through each cell sheet from the first surface to the second surface thereof, all the bores being hori~-nt~lly ` 2039302 _ aligned and located subst~nti~lly the same distance below the top edges of the cell sheets, at least one flexible strin er ext~n<ling through the bores, and a plurality of rigid tubes of a~plox;.,.~tely the same length subst~nti~lly equal to the same width W, each tube being positioned over the stringer 5 within one of the cells forming a spacer elçment between opposed snrf~ces of the cell sheets defining the filter cell wherein each tube is positioned.
More specifically the width W of the seriate cells is 8" to 20" and the spacer means includes one or more _exible stringers having a length E.G., 3W or more, such that they extend through a plurality of the cell sheet 0 bores, whereby they span mllltiple cells of the filter system~ e.g., 3 or morecells. In a plcfe -cd embodiment the stringers are flexible rods or tubes of diameter D, e.g., PVC tubes of about 0.25" - 0.50" diameter with a length of l0to30feet.
There are a plurality of rigid tubes of applox;...~tely the same length s~lbst~nti~lly equal to the width W of the cells. One such tube is positioned in each of the filter cells around the stringer and in between the respective exposed sllTfaGes of the cell sheets dçfining the cell in qnestion In a plcrellcd embodiment the rigid tubes are PVC tubes of about 0.50" -l" diameter.
In a plcrellcd embodiment the first and second side walls of the filter tank each incl~lde a grouted buttress in which an all-thread rod is enG~ed with one end thereof ext~ndin~ into the filter cell adjacent the buttress. Such rod extçnsions at the first and second side walls comprise the extreme ends of the stringers in the spacer means of the filter system.
Between these extreme ends, one or more flexible rods or tubes as previously mentioned form the stringer or stringers around which the aforesaid rigid tubes are positioned.
In another embodiment of the invention, a single s1Tinger is a rod that çxt~nds through all the bores in the cell sheets and the first and second 3 o side walls. The length of rod is such that its ends extend a short distance beyond the side walls, such ends are threaded and nuts are threaded on the both ends of the rod.
Several arr~ngement~ may be used to provide junctions between stringers in those embodiment~ where there are a plurality of stringers, 3 5 rather than one.

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-Typically a plurality of the spacer means of the invention will be used in each filter system spaced apart along the length of cell sheets in order to provide full protection a~in~t bowing of the cell sheets.

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BRIEF DESCRIPTION OF THE DRAWINGS
2 A more complete understanding of the invention can be obtained by 3 refelellce to the acconlpallyillg drawings in which:

4 FIG. 1 is an isometric sectional view of an automatic backwash filter system of the prior art which are im~loved by the cell sheet in~t~ tions of the 6 invention.
7 FIG. 2 is a fragmentary, sectional view showing a prior art system for 8 preventing bowing of cell sheets in filter sy~lellls as illustrated in FIG. 1.
g FIG. 3 is a fragmentary, sectional view of a first embodiment of an improved cell sheet in.~t~ tion of the invention in a filter system as illustrated 11 in FIG. 1.
12 FIG. 4 is a a fragmentary, sectional view of a second first embodiment 13 of an i.llploved cell sheet in~t~ tion of the invention in a filter system as 14 illustrated in FIG. 1.
FIG. 5 is a fragmentary, sectional view of a third embodiment of an 16 illl~lovt;d cell sheet in~t~ ti-~n of the invention in a filter system as illustrated 17 in FIG. 1.
18 FIG. 6 is a diagr~mm~tic view of a prefelled method for installation of 19 the stringers in the spacer means for filter systems of the invention.
2 o DESCRIPTION OF THE PREFERRED EMBODIMENTS
21 Referring in detail to the drawings, FIG. 1 illustrates a known 2 2 automatic backwash filter system 2 colllpli~illg a filter tank 4 having a bottom 2 3 6, first and second opposed, parallel side walls 8 & 10 respectively and third 24 and fourth opposed parallel side walls 12 & not shown respectively. The walls 8 & 10 each COlllplisc a grouted buttress 13.
2 6 The tank 4 is divided into a multiplicity of seriate cells 16 of2 7 sub~lalllially the same width W by a plurality of substantially vertical 28 rectangular cell sheets 18 of sllbst~ntially the same thickness. Sheets 18 have a 2 9 top edge 20, a bottom edge 22, a pair of side edges 24, a first exposed surface 3 o 26 on one side and a second exposed surface 28 on the other side of each the 31 sheet 18.
3 2 The cell sheets 18 run parallel to the first and second side walls 8 & 10 33 and each of the cells 18 contains a huli~onlal rigid porous filter plate 30 3 4 located between the exposed surfaces 26 & 28 of its respective cell sheets at a position above the tank bottom 6. Lugs 34 serve to support the plates 30 and angle members 36 hold them in position against the force of fluid flow through 2 the cells 16.
3 Filter media 32 is colllained in the cells 16 and supported on the 4 porous plates 30. The media 32 in FIGs. 2 - 5 is not hatched for the sake of clarity.
6 Influent means (not shown) delivers liquid to be filtered to the top of 7 the filter media as indicated by the arrows "I" and effluent means (not shown) 8 discharges liquid filtered through the media 32 and the plates 30 from the g filter system 4 at a level below the plates 30 as indicated by the arrows "E".
In operation of filter systems 2, a washwater hood 38 cooperates with 11 additional washwater means (not shown) to move backwash water in the 12 direction of arrows "B" up through the plate 30 and media 32 in the cell 16x 13 immediately below the hood 38. Meanwhile, in all the other cells 16, the flow 14 of water is downward as inrlic~te~l by arrows "I" and "E".
If the cell sheets 18 are installed in the tank 4 without some form of 16 lateral restraint along their length (illustrated in FIG. 1), they will tend to bow 17 and cause problems as previously indicated. FIG. 2 illustrates how such lateral 18 rei,llailll has been applied in prior known filter systems 2A.
19 In the filter system 2A of FIG. 2, tie rod assemblies 40 are used to mitigate bowing or deflection of the cell sheets 18A. These assemblies 21 colllpri~e bolts 42 threaded at both ends 44. Such ends 44 are inserted through 22 bores 46 in the cell sheets 18A. Then, four washers 48 and four nuts 50 are 23 applied and tightened to complete each assembly 40 to provide the desired 24 protection against bowing or deflection of the cell sheets 18A, particularly 2 5 during the backwash mode as described above relative to filter cell 16x.
2 6 As can be seem, two bores 46 are required in each cell sheet 18A in the 27 filter ~lellls 2A. Further, each assembly 40 must be installed one piece at a 2 8 time and before the nuts may be tightened and locked, a precise measulement 29 must be made by the installer.
FIG. 2 shows on embodiment of the imploved filter cell sheet spacer 31 means 52 of the invention in a filter system 2B.
32 The spacer means 52 colllplises fewer parts than prior art assemblies 33 40, namely, stringer 54, a plurality of tubes 60 of substantially the same length 34 equal to the width W of the cells 16B and a single bore 46 through each cell 3 5 sheet 18B. In the event a slight adjustment to the length of a tube 60 is needed to span a particular cell 16B, an annular shim 62 may be used.
2 The side wall 10B of the filter system 2B has a grouted bullless 13B in 3 which an all-thread rod 64, e.g., SS metal or the like, has been embedded in 4 conslluction of the wall 10B. The end 66 of rod 64 extends through the cell sheet 18B into the filter cell 16B and forms an extreme end of the stringer 54 6 of the spacer means 52. The rod 64 also serves the function of supporting the 7 outside cell sheet 18B during the pour of the grouted bulllcss 13B.
8 In a second embodiment, the filter system 2C colnplises cells 16Cg defined by cell sheets 18C having bores 46 therein and spacer means 52C.
The spacer means 52C comprises rigid tubes 60 and stringers 54a and 11 54b whose ends 55a & 55b approach one another. The rigid tube 60C, which 12 surrounds the stringers 54a and 54b and the space between the ends 55a &
13 55b, is split. Pipe clamps 68 are applied around the split tube 60C in the 14 region of ends 55a & 55b to force the split tube 60c into contact with the stringers 54a & 54b to create, in effect, a single stringer from two sections 54a 16 &54b.
17 The third embodiment of the invention shown in FIG. 5 illustrated18 another arrangement for m~king the final connection of stringers that do not 19 extend the full width of a filter system to which the new spacer means are 2 o applied.
21 The filter system 2D col"p,ises cells 16D defined by cell sheets 18D
2 2 having bores 46 therein and spacer means 52D that include rigid tubes 60 and 2 3 stringers 54 that do not extend into the filter cell 16Z. In order to complete the 24 assembly of the spacer means 52D in the cell 16Z, an all-thread rod 702 5 carrying a pair of nuts 72 and washers 74 is extended through the bores 46 in 26 the cell sheets 18D defining the cell 16Z. Then the nuts 72 are adjusted to 27 compress to facing walls of the cell sheets 18D against the nuts 72 and the 2 8 opposite walls against the respective rigid tubes 60.
2 9 FIG. 6 illustrates the relatively simple manner in which the new spacer means of the invention can be accomplished in the field. With wall 8B, 3 1 grouted bulll~ ss 13B, all-thread rod 64 and cell sheets 18B of the filter system 32 2B in place, a rigid tube 60 is positioned in the left most filter cell 16B and 33 over the exposed end 66 of rod 64. Then, at some suitable location between 34 the sidewalls of the filter system 2B, a second rigid tube 60' is positioned between a pair of cell sheets 18B' so that a flexible stringer 54 can be fed ` 2039302 through a bore (not shown) in one of the sheets 18B' and the tube 60'. This 2 operation is then repeated ~-vith sl1cceCcive cells and additional tubes 60' (not 3 shown) until the leading end of tube 60' reaches the cell containing the tube 60 4 thereby creating an arrangement as illustrated in FIG. 3. Next, the other s direction in the filter system 2B can have spacer means 52B installed by 6 repeated positioning of more rigid tubes 60" and another stringer 54". Finally, 7 the inct~ tion can be completed by m~king a final connection in the filter cell 8 used for the feeding of the stringers 54 & 54" as shown in FIGs. 4 or 5.
g The spacer means inct~ tions of the invention greatly simplify filter system assembly, reduce number of parts, insures greater accuracy and 11 reduces costs as co~ aled to the prior art. The rigid tubes 60 are precut to 12 the required length in the supplier's shop so field measurement is unnecessary 13 and the inct~ tion of the stringer or stringers does not require any time 14 con~uluillg, detailed mea~ulelllents.

Claims (5)

1. In an automatic backwash filter system including a filter tank defined by a bottom, first and second opposed, parallel side walls and third and fourth opposed parallel side walls divided into a multiplicity of seriate cells of substantially the same width W by a plurality of substantially verticalrectangular cell sheets defined by a top edge, a bottom edge, a pair of side edges, a first exposed surface on one side and a second exposed surface on the other side of each said cell sheet, said cell sheets running parallel to said first and second side walls, each of said cells containing a horizontal rigid porous filter plate located between said exposed surfaces of its said respective cell sheets at a position above said tank bottom, filter media contained in said cells and supported on said porous plates, influent means for delivering liquid to be filtered to the top of said filter media and effluent means for discharging liquid filtered through said media and said plates from said filter system at a level below said plates, the improvement which comprises:
spacer means to mitigate bowing of said cell sheets, said spacer means including:
bores extending through each cell sheet from said first surface to said second surface thereof, all said bores being horizontally aligned and located substantially the same distance below said top edges of said cell sheets, at least one flexible stringer extending through said bores, and a plurality of rigid tubes of approximately the same length substantially equal to said same width W, each said tube being positioned over said stringer within one of said cells forming a spacer element between opposed surfaces of the cell sheets defining the filter cell wherein said each tube is positioned.

2. In an automatic backwash filter system including a filter tank defined by a bottom, first and second opposed, parallel side walls and third and fourth opposed parallel side walls divided into a multiplicity of seriate cells of substantially the same width by a plurality of substantially vertical rectangular cell sheets of substantially the same thickness defined by a top edge, a bottom edge, a pair of side edges, a first exposed surface on one side and a second exposed surface on the other side of each said sheet, said cell sheets running parallel to said first and second side walls, each of said cells containing a horizontal rigid porous filter plate located between said exposed surfaces of its respective cell sheets at a position above said tank bottom, filter media contained in said cells and supported on said porous plates, influent means for delivering liquid to be filtered to the top of said filter media and effluent means for discharging liquid filtered through said media and said plates from said filter system at a level below said plates, the improvement which comprises:
spacer means to mitigate bowing of said cell sheets, said spacer means including:
bores extending through each cell sheet from said first surface to said second surface thereof and through said first and second side walls, all said bores being horizontally aligned a short distance below said top edges of said cell sheets, a stringer slightly longer in length than the distance between the outside surfaces of said first and second walls extending through all said bores, a tube of substantially the same length as said width of said cells positioned within each cell over said rod in between the exposed surfaces of the cell sheets defining said each cell, said stringer being fastened at both ends thereof between said first and second side walls.

3. In an automatic backwash filter system including a filter tank defined by a bottom, first and second opposed, parallel side walls and third and fourth opposed parallel side walls divided into a multiplicity of seriate cells of substantially the same width W by a plurality of substantially verticalrectangular cell sheets defined by a top edge, a bottom edge, a pair of side edges, a first exposed surface on one side and a second exposed surface on the other side of each said cell sheet, said cell sheets running parallel to said first and second side walls, each of said cells containing a horizontal rigid porous filter plate located between said exposed surfaces of its said respective cell sheets at a position above said tank bottom, filter media contained in said cells and supported on said porous plates, influent means for delivering liquid to be filtered to the top of said filter media and effluent means for discharging liquid filtered through said media and said plates from said filter system at a level below said plates, the improvement which comprises:

spacer means to mitigate bowing of said cell sheets, said spacer means including:
bores extending through each cell sheet from said first surface to said second surface thereof, all said bores being horizontally aligned and located substantially the same distance below said top edges of said cell sheets, a first flexible stringer extending through a first portion of said bores, a second flexible stringer extending through a second portion of said bores, a plurality of rigid tubes of the same length substantially equal to said same width W, each said rigid tube being positioned over one of said stringers within one of said cells forming a spacer element between opposed surfaces of the cell sheets defining the filter cell wherein said each tube is positioned, and additional spacer means within those cells of said filter system that do not contain one of said rigid tubes forming a spacer element between opposed surfaces of the cell sheets defining the filter cell lacking one of said rigid tubes.

4. The filter system of claim 3 wherein said additional spacer means comprises a all-thread rod and first and second nuts threaded thereon, said first nut applying pressure to one wall of said cell containing said all-thread rod and said second nut applying pressure to the opposite wall of said cell containing said all-thread rod.

5. The filter system of claim 3 wherein said additional spacer means comprises one of said rigid tubes having a longitudinal slot therein positioned around abutting ends of said first and second stringers and clamp means compressing said slotted tube into contact with said abutting ends.